Delta-Sigma Clock Divider Modulation for Lower EMI Peaks
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Solution Overview
Problem
High-frequency clock signals in modern systems lead to Electro Magnetic Interference (EMI), causing system failures due to their high energy and narrow bandwidth, which existing technologies fail to adequately address.
Innovation Solution
A spread spectrum clock generating circuit that adjusts the oscillation signal's frequency by controlling the dividing ratio using a delta-sigma modulator, generating a variable sub dividing ratio to distribute energy across a broader frequency band, thereby reducing EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the clock signal frequency is increased to operate the system at higher speed, then the productivity is improved, but the electro magnetic interference becomes more severe
Solution Approach 1:
The patent applies parameter changes by modulating the clock signal frequency around its nominal value. The frequency is varied within a spread spectrum range (e.g., ±0.5% to ±5% of the nominal frequency) to distribute the energy spectral density across a broader frequency band, thereby reducing EMI while maintaining the system's high-speed operation capability
Solution Approach 2:
The patent implements dynamics by continuously varying the clock frequency in a controlled manner rather than maintaining a fixed frequency. This is achieved through frequency modulation techniques where the clock signal frequency is dynamically adjusted according to a modulation signal, transforming the static high-frequency clock into a dynamic spread spectrum clock signal
2Productivity
If the clock signal frequency is increased to process digital data of large capacity, then the productivity is improved, but the energy concentration at a specific frequency increases causing EMI
Solution Approach 1:
The patent changes the frequency parameter of the clock signal by modulating it with a spread spectrum technique. This causes the energy that would otherwise be concentrated at a single high frequency to be distributed across a range of frequencies, reducing the energy density at any specific frequency point while preserving the overall data processing capability
Solution Approach 2:
The patent converts the harmful effect of concentrated high-frequency energy into a beneficial spread spectrum signal. By intentionally introducing frequency modulation, the concentrated energy peak is transformed into a distributed energy spectrum, turning the EMI problem into an opportunity to achieve both high data processing capacity and reduced electromagnetic interference
Data Source
AI summary
Provided is a spread spectrum clock generating circuit. The spread spectrum clock generating circuit includes: a phase detector receiving a reference frequency signal from the external and detecting a phase difference between the reference frequency signal and a frequency-divided signal; a voltage controlled oscillator outputting an oscillation signal corresponding to a detection result of the phase detector; a main divider generating the frequency-divided signal by dividing a frequency of the oscillation signal by a main dividing ratio; and a dividing ratio controller generating a variable count value, generating a sub dividing ratio by performing delta-sigma modulation according to the count value, and adjusting the main dividing ratio according to the sub dividing ratio.